Skip to Main Content
Skip Nav Destination
GEOREF RECORD

Structure, inferred mechanical properties, and implications for fluid transport in the decollement zone, Costa Rica convergent margin

Harold Tobin, Paola Vannucchi and Martin Meschede
Structure, inferred mechanical properties, and implications for fluid transport in the decollement zone, Costa Rica convergent margin
Geology (Boulder) (October 2001) 29 (10): 907-910

Abstract

Faults in a variety of tectonic settings can act as both conduits for and barriers to fluid flow, sometimes simultaneously. Documenting the interaction between hydrologic and tectonic processes in active faults in situ is the key to understanding their mechanical behavior and large-scale fluid transport properties. We present observations of the plate boundary decollement zone at the Middle America Trench off Costa Rica, showing that it is structurally divisible into an upper brittle-fracture-dominated domain overlying a lower, ductile domain. Pore-water geochemical evidence shows that along-fault flow is occurring specifically in the upper brittle domain, but is hydrologically isolated from fluids in the underlying footwall sediments. We propose a model for the mechanics of these contrasting domains in which differing stress paths coexist in the upper and lower parts of the decollement zone. The data suggest a mechanically controlled permeability anisotropy at a scale of several meters to approximately 10 m across the decollement zone. This documentation of separate yet simultaneously active mechanical and hydrologic subregimes within a decollement provides a relatively simple explanation for enhanced along-fault permeability coexisting with reduced cross-fault permeability, without requiring matrix-scale permeability anisotropy.


ISSN: 0091-7613
EISSN: 1943-2682
Coden: GLGYBA
Serial Title: Geology (Boulder)
Serial Volume: 29
Serial Issue: 10
Title: Structure, inferred mechanical properties, and implications for fluid transport in the decollement zone, Costa Rica convergent margin
Affiliation: New Mexico Institute of Mining and Technology, Department of Earth and Environmental Science, Socorro, NM, United States
Pages: 907-910
Published: 200110
Text Language: English
Publisher: Geological Society of America (GSA), Boulder, CO, United States
References: 17
Accession Number: 2001-073328
Categories: Solid-earth geophysicsOceanography
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. sects., sketch map
N09°38'23" - N09°38'23", W86°12'00" - W86°12'00"
N09°39'16" - N09°39'16", W86°11'09" - W86°11'09"
N09°39'43" - N09°39'43", W86°10'45" - W86°10'45"
Secondary Affiliation: Universita di Modena, ITA, ItalyUniversity of Tuebingen, DEU, Federal Republic of Germany
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2019, American Geosciences Institute. Reference includes data supplied by the Geological Society of America, Boulder, CO, United States
Update Code: 200123
Program Name: ODPOcean Drilling Program
Close Modal

or Create an Account

Close Modal
Close Modal